Innovative and Durable New Green House Farming Technology
Arid Greenhouse is suitable for deployment anywhere in the world, but its credentials are most significant in coastal, river and lake environments in arid/semi-arid regions. Most regions in South Africa are arid/semi-arid or traditionally outside the extent of open horticulture.
Our Innovative Greenhouse Farming project is aimed at increasing organic quality, health, safety and continuous volumes of protected horticulture products in South Africa. It also aims at using solar energy for desalination, distillation and electricity generation.
Arid Greenhouse closed horticulture technology offers energy savings and volumes of scale opportunities non-existent with existing ‘pad and fan’ technologies, which are inefficient and uneconomical to operate in arid coastal areas with high ambient relative humidity like in the Western Cape in South Africa. Arid Greenhouse can provide for the production of high value protected horticulture products, solar desalination and online marketing which will result in the creation of employment allowing for long term development and wealth for traditional communities.
Protected horticulture has many advantages over traditional open horticulture.
- Productivity can be increased by more than fivefold per unit of land, water, energy, and labour
- Crops can be produced year round regardless of season, whereby multiple cropping on the same unit of land is possible. The flexibility of the system means that farmers can take advantage of market seasonality and higher prices
- Protected agriculture can reduce environmental degradation by reducing the amount of water and fertilizers used to grow the product and by reducing the potential contamination of ground water by fertilizers, insecticides, fungicides and other chemicals
- Protective housing provides more protection for high value crops from unfavourable weather conditions, pests and diseases
- Eliminating the use of the toxic pesticides and insecticides with biological pest control, aimed at preventing infestation and use of non-toxic controls
- Glasshouse crops obtain better quality and higher prices in the market while produced with less amount of water
- Increase of income per unit of water and land.
Other advantages of the New Green House Farming Technology "Always Closed Windows Glasshouse" concept are the shielding of pesticides and harmful particles from the external environment. When required, Arid Greenhouse allows for a 100 per cent biological pest control inside the glasshouse, without the need for ‘dusting’ with insecticides.
In chemical horticulture, a specific insecticide may be applied to quickly kill off a particular insect pest. Chemical controls can dramatically reduce pest populations in the short term. However, by unavoidably killing or starving natural control insects and animals, chemicals can cause an increase in the pest population in the long term.
Repeated use of insecticides and herbicides also encourages rapid natural selection of resistant insects, plants and other organisms, necessitating increased use, or requiring new, more powerful controls. In contrast, protected horticulture with biological pest control implies that some pest populations are tolerated. However, this requires a thorough understanding of pest life cycles and interactions, involving the cumulative effect of many techniques like allowing for an acceptable level of pest damage; encouraging predatory beneficial insects to flourish and eat pests; encouraging beneficial microorganisms; careful plant selection, choosing disease-resistant varieties; planting companion crops that discourage or divert pests; rotating crops to different locations from year to year to interrupt pest reproduction cycles; using insect traps to monitor and control insect populations.
Each of these New Green House Farming Technologies also provides for other benefits, such as soil protection and improvement, fertilization, pollination, water conservation and season extension. These benefits are both complementary and cumulative in overall effect on site health. Biological pest control, when required, will be part of Arid Greenhouse’s integrated pest management (IPM).
As an IPM is related to the intensive nature of glasshouse horticulture following research and development is required like breeding and cultivar testing; production of plants; extended growing seasons; crop rotation and fallow; soil and water management; soil health; crop health; weed control; crop management; product quality, safety and healthiness; energy use and management; economic, social, ecological and environmental implications; standards and certification.
Closed glasshouses require substantial cooling power to dissipate the insulation of heat. Therefore, only cooling with ‘free’ coolant supplies like seawater or river and lake water renders a closed glasshouse economically feasible. Dependent upon the environment, coolant requirement for Arid Greenhouse constitutes around 400 m3 per hour per hectare of glasshouse floor.
Arid Greenhouse’s cooling system controls both the glasshouse atmosphere’s temperature, sensible heat, and the glasshouse’s relative humidity (RH), or latent heat. A constant RH control is unknown in conventional glasshouse technologies.
Many known fungus diseases caused by extreme RH like Botrytus can therefore be avoided. An automated air condition controller assigns part of the cooling wall either for sensible heat removal ‘duty’ or latent heat removal ‘duty’.
High efficiency in energy consumption is achieved by the storage of refrigerated water in reservoirs, eliminating a continuous refrigeration requirement and increasing the coefficient of performance (COP) of Arid Greenhouse’s cooling system.
The sensible and latent heat control system in a Arid Greenhouse glasshouse is similar to a distillation process under atmospheric pressure. The plants can be considered as the evaporator and the cooling walls as the condenser. Irrigation water is evaporated by the plants in the glasshouse atmosphere.
The double cooling wall fans circulate the moisture enriched atmosphere inside the glasshouse, whereby water vapor is transported to the cooling walls, where part of the moisture is condensed out of the air. To keep the RH in the glasshouse at a constant level, the exact amount of water evaporated by the plants is condensed in the cooling wall. This condensed water is collected, treated and used again for irrigating the plants with little need of additional irrigation supply.
Arid Greenhouse’s solar desalination technology is based on adiabatic solar evaporation, whereby warm and dry air passes over a moist surface shaped like a pad.This pad is composed of special materials in the form of cellulose or glass fibers with a geometry that maximizes the surface area over which the air passes.
This type of evaporation is called adiabatic because no external heat source is used to evaporate the water. Only the heat content of the air supplies the energy for the thermodynamic cycle. In Arid Greenhouse’s proprietary setup, the moist air from the evaporation pads is led by fans through Arid Greenhouse’s cooling walls, which function as cold heat exchangers where water vapor from the wet air condenses on its surfaces.
To enable heat removal, cooling water is introduced to the cooling walls in order to facilitate heat removal. The condensate can be collected and used as fresh water output. The pad system introduces extra water vapor in the glasshouse atmosphere, whereby the latent heat content will increase with the sensible heat content decreasing in equal proportion.
As a result, the pads assist in lowering the glasshouse atmosphere temperature, effectively functioning as an additional cooling system. The total amount of (additional) potable water produced in this way is around 2mln liters per ha Arid Greenhouse glasshouse floor per year.
For further inquiries feel free to contact pieter@aridgreenhouse.com
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